Unjust damage to the reputation of a person can have devasting effects. Untruths told and spread may injure a person's employment, relationships, friendships, and even one's own confidence, self-esteem, and trust of others. For these reasons, the law bears heavily upon those persons who speak falsely about other persons.
Defamation can arise from one of two methods. Libel involves disparagement by written words and slander involves disparagement by spoken words. In Ontario, the common law as well as the Libel and Slander Act, R.S.O. 1990, c. L.12 apply to legal cases involving defamation.
A legal case involving defamation often involves the key question of whether a statement was actually made and if so, whether the statement was defamatory. In law, the definition of defamation is very broad. Accordingly, once shown that a statement was made, a lawsuit then considers whether the statement was defamatory.
The legal test of whether a statement is defamatory is simply based on the question of whether the words were likely, "to lower the plaintiff in the estimation of right-thinking members of society generally" as per Lord Atkin in Sim v. Stretch,  2 All E.R. 1237 at 1240 and accepted in dozens of Canadian cases as per a quick search via the CanLII.org website.
It is important to note that the definition of what is defamatory omits the requirement that the words were actually defamatory; accordingly, a successful defamation case may result merely by demonstrating that general members of society would find the words defamatory rather than a need to demonstrate that the actual person, or persons, to whom the words were passed actually believed the words and diminished views of the person whom the defamatory words were about. For this reason, a successful defamation case may arise despite the fact that the words were passed to a person who disbelieves the words and is devoid of any reduction in regard to the reputation of the person about whom the words were spoken. A defamation case is without need of actual harm as per O'Malley v. O'Callaghan, 1992 CanLII 6090 (AB QB). Additionally, an intent to cause harm to the reputation of another is unnecessary to a defamation lawsuit per Stopforth v. Goyer, 1979 CanLII 1661 (ON CA).
With the above said, one must bear in mind that not all untrue and unflattering words are deemed defamatory. In a defamation case, the context of the situation in which the words were passed in addition to the words themselves are considered. A heated debate wherein one person states that the another person is an "idiot" while in the presence of other persons is unlikely to found a successful legal case as 'right-thinking members of society' would likely recognize the inflamatory nature of the debate with a corresponding disregard to the statement and therefore lack of any lowering of reputation (Klar, Lewis: Tort Law (3d) at 675).
Truth of defamatory words provides a justified reason for uttering or publishing words that are defamatory. Essentially, while the words may defame in the sense that the words, "lower the plaintiff in the estimation of right-thinking members of society", where the words are true, such 'lowering' occurs due to the genuine conduct of the Plaintiff rather than the telling of the conduct by the Defendant. On this basis, the spreading of truthful rumours may be lawful from the 'defamation' point of view; however, do see 'breach of privacy' concerns, among other things). It is necessary to note that when mounting a justification defence on the basis of truth, such must be pleaded at the outset. Furthermore, it is the 'sting of words' beyond just the actual words that must be proven true; Garrett v. Mikalachki, 2000 CarswellOnt 1298:
130 The defendants did not plead justification which is a prerequisite to relying on a defence that the words were true: Manitoba Free Press Co. v. Martin (1892), 21 S.C.R. 518 (S.C.C.).
131 In any event, such a defence would fail here because the burden is on the defendants to prove that the sting of the words is true and they have not done so.
Qualified Privilege Exception
In certain circumstances, there may exist an occasion where a person bears a duty or right to issue a document or utter a statement that is defamatory of another person. Such occasions may involve a council meeting, court action, election campaign, among other things. In such circumstances, a 'qualified privilege' exists whereby documents or statements may be defamatory without risk of liability by virtue of the balancing of the right to freedom of speech and opinion versus the right of protection from defamation.
Per the Supreme Court in Botiuk v. Toronto Free Press Publications Ltd.,  3 S.C.R. 3 at paragraph 79:
“[w]here an occasion is shown to be privileged, the bona fides of the defendant is presumed and the defendant is free to publish remarks which may be defamatory and untrue about the plaintiff”.
Accordingly, where the Defendant speaks or writes mala fide, the qualfied privilege fails and liability may apply. It is notable that the burden of proof that words were mala fide is placed upon the Plaintiff. This results in a shifting back and forth of various burdens. Initially, the Plaintiff must simply prove that words were spoken that, "... lower the plaintiff in the estimation of right-thinking members of society ...", per Sim case as above. The Defendant would then bear the burden of proving that such words were true and therefore permissible; however, if such words were untrue yet arising within a 'qualified privilege' occasion, the Defendant receives a 'free pass' unless the mala fide utterance is proven by the Plaintiff; per Hill v. Church of Scientology of Toronto,  2 S.C.R. 1130:
144 The legal effect of the defence of qualified privilege is to rebut the inference, which normally arises from the publication of defamatory words, that they were spoken with malice. Where the occasion is shown to be privileged, the bona fides of the defendant is presumed and the defendant is free to publish, with impunity, remarks which may be defamatory and untrue about the plaintiff. However, the privilege is not absolute and can be defeated if the dominant motive for publishing the statement is actual or express malice. See Horrocks v. Lowe,  A.C. 135 (H.L.), at p. 149.
145 Malice is commonly understood, in the popular sense, as spite or ill‑will. However, it also includes, as Dickson J. (as he then was) pointed out in dissent in Cherneskey, supra, at p. 1099, "any indirect motive or ulterior purpose" that conflicts with the sense of duty or the mutual interest which the occasion created. See, also, Taylor v. Despard, 1956 CanLII 124 (ON CA) ,  O.R. 963 (C.A.). Malice may also be established by showing that the defendant spoke dishonestly, or in knowing or reckless disregard for the truth. See McLoughlin, supra, at pp. 323‑24, and Netupsky v. Craig, 1972 CanLII 19 (SCC) ,  S.C.R. 55, at pp. 61‑62.
146 Qualified privilege may also be defeated when the limits of the duty or interest have been exceeded. See The Law of Defamation in Canada, supra, at pp. 13‑193 and 13‑194; Salmond and Heuston on the Law of Torts (20th ed. 1992), at pp. 166‑67. As Loreburn E. stated at pp. 320‑21 in Adam v. Ward, supra:
. . . the fact that an occasion is privileged does not necessarily protect all that is said or written on that occasion. Anything that is not relevant and pertinent to the discharge of the duty or the exercise of the right or the safeguarding of the interest which creates the privilege will not be protected.
147 In other words, the information communicated must be reasonably appropriate in the context of the circumstances existing on the occasion when that information was given. For example, in Douglas v. Tucker, 1951 CanLII 54 (SCC),  1 S.C.R. 275, the defendant, during an election campaign, stated that the plaintiff, who was the officer of an investment company, had charged a farmer and his wife an exorbitant rate of interest causing them to lose their property. The plaintiff maintained that the allegation was without foundation. In response, the defendant asserted that the plaintiff was facing a charge of fraud which had been adjourned until after the election. This Court held that the defendant had an interest in responding to the plaintiff's denial, thereby giving rise to an occasion of qualified privilege. However, it ruled that the occasion was exceeded because the defendant's comments went beyond what was "germane and reasonably appropriate" (p. 286).
Proof of Malice
The Plaintiff may seek to prove malice in a number of ways including express malice where the words are plainly and obviously of a malicious intent. Malice can also be proven by showing that the Defendant holds a personal vendetta against the Plaintiff and that a reckless disregard for truth may be sufficient in establishing malice; Todd v. Everett, 2014 ONSC 1322:
 Certainly if there was evidence from which a trier of fact could draw the inference that the Defendant acted with reckless disregard for the truth or the Defendant’s actions were motivated by a personal vendetta against the Plaintiff that would be a basis for a finding of malice. The issue raised on this appeal is whether there was any evidence to this effect or any other evidence that would justify a finding of malice.
Disregard for the Truth
 On this point the Deputy Judge found as follows:
[The Defendant] had a total disregard for the truth and indeed had a total disregard for the consequences … He had every opportunity to verify the truth and chose not to … It would have been a simple task to verify the truth by speaking to the plaintiff or Mr. Currie but he chose not to … All these incidents occurred without a tittle of evidence to support the allegations.
It is important to take heed that 'proof of malice' requires demonstrating that a 'belief of truth' regarding was false or reckless. Malice requires more than mere carelessness whereas 'belief of truth' about a fact may be honestly held despite carelessness in coming to the belief per Botiuk:
96 A distinction in law exists between "carelessness" with regard to the truth, which does not amount to actual malice, and "recklessness", which does. In The Law of Defamation in Canada, supra, R. E. Brown refers to the distinction in this way (at pp. 16‑29 to 16‑30):
. . . a defendant is not malicious merely because he relies solely on gossip and suspicion, or because he is irrational, impulsive, stupid, hasty, rash, improvident or credulous, foolish, unfair, pig‑headed or obstinate, or because he was labouring under some misapprehension or imperfect recollection, although the presence of these factors may be some evidence of malice.
97 The author then puts forward the reasons of Lord Diplock in Horrocks v. Lowe,  A.C. 135 (H.L.), as representative (though not definitively) of the Canadian position. In that case Lord Diplock wrote at p. 150:
. . . what is required on the part of the defamer to entitle him to the protection of the privilege is positive belief in the truth of what he published or, as it is generally though tautologously termed, "honest belief". If he publishes untrue defamatory matter recklessly, without considering or caring whether it be true or not, he is in this, as in other branches of the law, treated as if he knew it to be false. But indifference to the truth of what he publishes is not to be equated with carelessness, impulsiveness or irrationality in arriving at a positive belief that it is true. . . But despite the imperfection of the mental process by which the belief is arrived at it may still be "honest", that is, a positive belief that the conclusions they have reached are true. The law demands no more. [Emphasis added.]
Whether the carelessness of a defamer rises to the level of recklessness requires a 'reasonable expectation' review of the conduct involved including the sophistication of the defamer and whether the defamer ought to diligently review a document or make adequate inquiries so to ensure truth prior to issuing or signing a document. This reasonable expectation in determining accuracy applies especially so to legal professionals when signing Declarations or Affidavit documents containing potentially defaming information; per Botiuk:
98 This proposition does indeed seem to be generally representative of the Canadian position on the matter. However, when the defendants are lawyers who must be presumed to be reasonably familiar with both the law of libel and the legal consequences flowing from the signing of a document, their actions will be more closely scrutinized than would those of a lay person. That is to say, actions which might be characterized as careless behaviour in a lay person could well become reckless behaviour in a lawyer with all the resulting legal consequences of reckless behaviour. That is the very situation presented in this case.
99 The appellant lawyers signed a Lawyers' Declaration which stated that they had "familiarized" themselves with the Report and that it "correctly and accurately" reflected the state of affairs during and after the Kosygin demonstration. Yet, several of them had not even read it. Most of them did not know anything about the preparation of Botiuk's account. Some neither talked to Botiuk before signing the Lawyers' Declaration nor discussed it with the others. As lawyers, they should have known how significant the impact of the Lawyers' Declaration would be on Botiuk. They were duty-bound to take reasonable steps to investigate and ensure that the document was correct.
100 In the Maksymec Reply, Maksymec referred to the Lawyers' Declaration as the basis for the statement that the various lawyers, including the appellants, gave generously of their time and assistance before and during the Vannini inquiry and that they had agreed not to charge for their work. Although the appellants knew that in reality they had contributed very little and that there could not have been any such agreement, they did nothing to correct the inaccurate impression left by the Maksymec Reply and raised no objection to Maksymec's subsequent use of the Lawyers' Declaration.
101 Although it is not determinative, the conduct of the appellant lawyers prior to and during the trial can properly be taken into consideration as an indication of their general attitude toward Botiuk. None of them apologized to him or retracted what was written in the Lawyers' Declaration. Rather, as the trial progressed and the true situation was revealed, each continued to maintain that the plaintiff was wrong. As the trial judge found, the appellants Zarowsky and Bardyn manifested hostility towards the plaintiff during their testimony, particularly in relation to the extent of Botiuk's participation at the inquiry. Despite the overwhelming evidence on this point, most of the lawyers were reluctant to acknowledge how little each of them had done and, conversely, how much Botiuk had given of his time and energy.
102 The appellants must have, or at the very least should have, realized that the endorsement of eight prominent lawyers would have a devastating effect on Botiuk's reputation. The evidence indicates that after the publication of the Lawyers' Declaration, public opinion in the community swung decisively against Botiuk. Witnesses testified that they became convinced that the rumours might actually be true after they had read the document.
Response to Defaming
It can actually be quite appropriate to respond to defamatory statements whereas publishing the defamatory statements so to enable clarifying public debate; Whitehead v. Sarachman, 2012 ONSC 6641 at paragraph 70:
... Mis-statements, overstatements and excessive language may be exposed and corrected through public debate, often in a more timely and effective manner than through the slow process of a civil action. ...
As it is nearly impossible to accurately ascertain an exact monetary value for damage to reputation, awards in defamation cases are generally 'at-large', meaning at the discretion of judge or jury (Klar, Lewis: Tort Law (3d) at 710). Further, where the defamation was malicious and harmful, significant aggravated damages and punitive damages may be awarded per Hill.